Abstract
Hyperparasitism is a normal behavior of parasitoids, which often happens among species. Conspecific hyperparasitism, such as some kinds of heteronomous hyperparasitic behaviors, has been only reported in some species belonging to Aphelinidae. In this article, the conspecific hyperparasitism of Pachycrepoideus vindemmiae (Pteromalidae) is reported, with Drosophila puparia as hosts. Hosts were exposed to P. vindemmiae females twice to parasitism with nine, twelve, and fifteen day intervals between the two exposures. None of the infested hosts emerged more than one offspring, and emergence of parasitoid offspring occurred in two obvious events, synchronously with the exposure time intervals, which suggested that offspring emerging during the first and second events would come from the primary and secondary parasitoids, respectively, and the inference with the developmental duration of offspring also indicated this. With two P. vindemmiae strains that could be identified by a simple sequence repeat marker, the above speculation of the origin of those offspring emerging during the two events was confirmed. Dissection of hosts exposed twice revealed a cannibalism behavior of larvae from the secondary foundresses on the primary conspecific pupae. Our results suggested a conspecific hyperparasitism behavior of the secondary parasitoids on the primary conspecifics. Measures showed a reduced body size for the adults from the conspecific hyperparasitism. Foundresses from the conspecific hyperparasitism had less fitness variables than those from primary parasitism, with shorter longevity, less life time fecundity, lower values of infestation degree, and lower success rate of parasitism. However, when the parasitoids from the conspecific hyperparasitism met healthy Drosophila puparia, their offspring would recover to normal size. Frequency of the conspecific hyperparasitism behavior enhanced with the decreasing of proportion of healthy hosts in the oviposition patch. The conspecific hyperparasitism of P. vindemmiae on the primary conspecifics would be helpful to last the population when healthy hosts are absent in the oviposition patch.
Highlights
Parasitoid wasps are insects whose larvae develop by feeding on the bodies of other arthropods, and larval feeding results in the death of the parasitoid’s host
Our results showed that the duration of P. vindemmiae offspring emergence can be divided into two obvious events after Drosophila puparia have been parasitized twice with nine, twelve and fifteen day intervals; the offspring at the later emerging event probably belonged to the secondary foundresses
With two P. vindemmiae strains which can be identified by an simple sequence repeat (SSR) marker, we further confirmed that those emerging in the later event were from the secondary foundresses
Summary
Parasitoid wasps are insects whose larvae develop by feeding on the bodies of other arthropods, and larval feeding results in the death of the parasitoid’s host. Hyperparasitism happens when a secondary female of another parasitoid wasp species lays her eggs on the host, but the larvae of the secondary species feed on the primary parasitoids [1]. Two kinds of hyperparasitism exist, normally known as facultative and obligate hyperparasitism. The former happens when hyperparasitoids can attack healthy hosts and hyperparasitism occurs only when eggs are laid on a previously infested host. The latter occurs when hyperparasitoids can only develop on the primary parasitoid larvae or pupae. Hyperparasitism often occurs among species, and multitrophic relationships exist in the food chains with several parasitoids, e.g. the system of pea aphid and parasitoid groups (reviewed in [2])
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